The present invention relates to mobile land vehicles having a boom assembly, and more particularly to vehicles used for felling and handling trees on steep mountainous terrain. The vehicle of this invention includes apparatus for providing multidirectional relative movement between a conventional tread assembly of the caterpillar type and a swing-house assembly which includes a boom subassembly supporting tree-felling and handling equipment, so that the swing-house assembly is maintained in a substantially level relationship with the horizontal, regardless of the inclination of the ground on which the vehicle rides, and so that the center of gravity of the vehicle is optimized by weight transfer corresponding to the type of ground inclination encountered.
In the past, the operation of conventional cranes, derricks and other land vehicles having a boom assembly mounted thereon was limited by the inclination of the ground during specific operations while the vehicle was stationary, and during movement of the vehicle over changing terrain when the vehicle is in motion. The limitation and operability of these conventional vehicles is pronounced when the vehicle is inclined in various positions on sloping ground, such as on hills or mountains. As is well known, such inclination of the vehicle shifts the center of gravity away from the point of maximum load stability of the vehicle on the ground which unbalances the vehicle thus tending to cause it to overturn if some correction is not made, as for example by movement of the vehicle itself, to reduce the critical deviation of the center of gravity from this maximum load stability point. Also, as can be appreciated, shifting of the center of gravity of the maximum load stability point likewise occurs during travel of the vehicle over uneven terrain having marked differences in grade.
Among the conventional devices of the type described above are those disclosed for U.S. Pat. No. 3,160,284 to Moore; U.S. Pat. No. 4,326,571 to Crawford; and U.S. Pat. No. 3,430,790 to Beltrami.
The patent to Moore discloses a weight-stabilizing, load-handling vehicle used in forestry work which is adapted to operate on inclined surfaces wherein the vehicle includes a swinghouse assembly 6, an engine 7 and a double cab 8, all mounted on a base platform 3 which rides on caterpiller treads 2. The machine includes a mechanism for moving the cab in fore and aft directions, as well as in right and left directions by means of dual stacked slide-track assemblies (as shown in FIGS. 4, 5, 7 and 8). In another embodiment, movement of the cab is possible in these directions by use of a tilting and sliding track assembly.
In the Crawford patent, there is disclosed a vehicle adapted for operation in hilly regions which utilizes two hydraulic cylinders to move and tilt the operator's cab in right and left directions. Also disclosed is a vehicle having the capacity of tilting the cab fore and aft using hydraulic cylinders.
In the Beltrami patent, an excavator is disclosed which includes a driver's cab 19 supported by a tiltable platform arrangement 14 where the platform is adapted for tilting movement in the fore and aft, and right and left, directions by means of four hydraulic cylinders and unparallel, articulated links.